1956 Topps grey back set
 

Not long ago I finished my 1956 Topps set and made a point of only having grey back cards for the entire set (a couple of series were printed in either grey or white back stock)

I know there's a slight value difference in the back stock between the series, that aside, would you put a premium on a set like that?

I'm not looking to sell by any means. Just curious. There are several sets in which a variety of back stock was used (1959 comes to mind) Do you look for coordination in the backs like that or does it not matter?

Cards #101-180 in white back command a premium. Somewhere between 20% and 300% premium depending on the card.